Describe the bug

Since #13752 the prose sections were moved to https://github.com/NixOS/nix/blob/master/src/libstore/s3-binary-cache-store.md but they do not appear in the manual.

Steps To Reproduce

Restore the s3 "fixes" in #14711

Expected behavior

Content is preserved.

Metadata

Additional context

Checklist

• checked latest Nix manual (source)
• checked open bug issues and pull requests for possible duplicates

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